Insulating porch ceiling
i have a question that I can’t seem to figure out a definitive answer to. I have an 1890’s brick home in Chicago that had an enclosed porch addition added on at some point, (probably 100 years ago). It’s not a big porch, maybe 7.5 feet deep by 18’ total across. The porch is 3 stories in total, a walk out lower portion a similar sized second level off of our apartment, and a section off of a walk up attic. I’d like to finish the the two top levels of the porch to add extra living space for my growing family. I’m confused about what to do with the attic ceiling. The roof was replaced by the former owners maybe 4-5 years ago and is in good shape. It has asphalt shingles over sheathing, which is laid over the original old roofing boards. The whole roof has old 4 inch rafters that are in good shape. The roof ends at the end of the house and there is no soffit or overhang and the roof is unvented. My original idea was to Cut and cobble 4” rigid foam in between the rafters since they are pretty straight. Foam and tape that, then take large uncut sheets of 2-3” rigid foam and go over everything horizontally. Tape that, then hang drywall over the foam. I also thought about adding a soffit box down the middle of the ceiling to add lights, and by doing so would be able to add insulation above it. I’m worried of course that I will damage my roof, or somehow compromise the porch. Is this a bad way of going about this? I apologize if I am not using the correct terms for everything. I’m relatively new to home ownership and looking to learn as much as I can.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part